x1, y1, x2, y2 = map(float, raw_input().split())
num = (x2-x1)*(x2-x1) + (y2-y1)*(y2-y1)
if num == 0:
    print 0
else:
    xi = num
    for _ in range(100):
        xi = (xi + (num / xi)) / 2.0
    print xi x1, y1, x2, y2 = map(float, raw_input().split()) x1 map(float, raw_input().split()) map float raw_input().split() ().split () raw_input split y1 x2 y2 num = (x2-x1)*(x2-x1) + (y2-y1)*(y2-y1) num (x2-x1)*(x2-x1) + (y2-y1)*(y2-y1) (x2-x1)*(x2-x1) x2-x1 x2 x1 x2-x1 x2 x1 (y2-y1)*(y2-y1) y2-y1 y2 y1 y2-y1 y2 y1 if num == 0:
    print 0
else:
    xi = num
    for _ in range(100):
        xi = (xi + (num / xi)) / 2.0
    print xi num == 0 num 0 print xi = num xi num for _ in range(100):
        xi = (xi + (num / xi)) / 2.0
     _ range(100) range 100 xi = (xi + (num / xi)) / 2.0 xi (xi + (num / xi)) / 2.0 xi + (num / xi) xi num / xi num xi 2.0 print num = (x2-x1)*(x2-x1) + (y2-y1)*(y2-y1) (x2-x1)*(x2-x1) + (y2-y1)*(y2-y1) num y1, x2, y2 = map(float, raw_input().split()) map(float, raw_input().split()) y1 x2, y2 = map(float, raw_input().split()) map(float, raw_input().split()) x2 y2 = map(float, raw_input().split()) map(float, raw_input().split()) y2 x1, y1, x2, y2 = map(float, raw_input().split()) map(float, raw_input().split()) x1 xi = num num xi xi = (xi + (num / xi)) / 2.0 (xi + (num / xi)) / 2.0 xi
x1, y1, x2, y2 = map(float, raw_input().split())
num = (x2-x1)*(x2-x1) + (y2-y1)*(y2-y1)
if num == 0:
    print 0
else:
    xi = num
    for _ in range(100):
        xi = (xi + (num / xi)) / 2.0
    print xi